Puff pastry and other laminated edible products have long been produced by processes which involve first forming a composite sheet in which one or more layers of fat (a term which is used herein to cover both fats which are solid at room temperature and those which are liquid at room temperature, the later normally being designated "oils") are sandwiched between layers of dough. This composite sheet is then laminated, that is to say a plurality of plies of the sheet are piled up on top of one another. Following this initial lamination, the laminated sheet is usually rolled to reduce its thickness, and then subjected to a second lamination. After this second lamination, the sheet is cut to the desired shapes and backed to produce an article comprised of a large number of very thin layers of the dough.
A variety of apparatus and processes are known for performing the operations of sheet formation, lamination and rolling used in such a process. For example, U.S. Pat. No. 3,151,987 to Colby discloses a method of making pastry and similar products in which flour and water are mixed to produce an extensible paste which is extruded into a sheet. Plastic shortening is applied to the sheet and the process is repeated to form a pile of sheets, which is then compressed to produce the final product.
U.S. Pat. No. 3,821,452 to Hayashi describes a process for producing multi-layered food products such as pies, danish pastries and sweet rolls. This process comprises forming spherical particles in which fat is enrobed by dough, feeding these particles one at a time on to a movable plate and flattening each particle individually, using a vertically oscillating platen, to form a pile of multiple layers. This pile is then moved to pinch rolls to reduce its thickness and to produce the final multi-layered product.
U.S. Pat. No. 4,453,906 to Hayashi describes a process for forming a continuous sheet of dough in which a mass of dough is held in a container, the bottom of which is closed by a conveyor. Movement of the conveyor causes a sheet of dough to be extruded through a slot between a cutter fixed to one wall of the container and the upper surface of the conveyor. The patent does not describe any way in which the process could be used for coextrusion of fat and dough, and it appears that the process could not be adapted to such coextrusion.
U.S. Pat. No. 1,975,326 to Loose et al describes a continuous sheeting and laminating process for producing crackers, in which dough is formed into a plurality of sheets by rollers, then layers of creams, fats, or mastics are spread onto the individual layers of dough and the layers of dough are piled on top of one another and passed between a second set of rollers. Thereafter, the combined multi-layered product is passed vertically downwardly between a third set of rollers into an oscillating frame which oscillates transversely across a conveyor, thereby depositing multiple layers of the product onto the conveyor. While on the conveyor, the resultant multi-layered sheet is passed between a pair of rollers which reduce the thickness of the sheet. Upon leaving the conveyor, the sheet passes downwardly between a further pair of rollers and through a second oscillating frame, which oscillates transversely across a second conveyor, again producing multiple plies of the multi-layered sheet upon the second conveyor. While on the second conveyor, the multiple plies are again rolled by a further pair of rollers.
U.S. Pat. No. 3,851,088 to Albrecht describes a method of laminating sheets of dough in which a sheet is passed through a pendulum assembly which oscillates transversely across a conveyor. The portion of the conveyor lying beneath the pendulum assembly is formed into a concave shape in order to keep the distance between the discharge end of the pendulum assembly and the conveyor constant. The oscillation of the pendulum assembly and the movement of the conveyor cause multiple plies of the sheet to be deposited on to the conveyor.
U.S. Pat. No. 1,868,317 to Green et al describes a process for laminating dough in which dough is fed from the end of a first conveyor, the discharge end of which passes around a roller, downwardly onto a second conveyor running at right angles to the first. An elaborate drive mechanism allows reciprocation of the roller at the discharge end of the first conveyor without tearing the dough, so that the sheet of dough falling from the first conveyor onto the second conveyor oscillates transversely across the second conveyor, so forming multiple plies of the sheet of dough on the second conveyor.
U.S. Pat. No. 2,823,625 to Oakes describes a method of laminating dough in which a sheet of dough is advanced endwise, the leading portion of the sheet is alternately stopped and advanced at a higher rate than the remainder of the sheet, the leading portion of the sheet is repeatedly cut off to produce a succession of smaller sheets and then these smaller sheets are deposited onto a second conveyor moving at right angles to the first with a large overlap between successive sheets, so producing multiple plies of the sheet on the second conveyor.
U.S. Pat. No. 4,113,412 to Hayashi describes a method of rolling dough using an assembly of rollers mounted on an endless belt which causes the axes of the rollers to move in the same direction as the dough, while the rollers rotate about their own axes such that the surfaces of the rollers in contact with the dough are moving in the opposite direction to the dough itself. An elaborate drive mechanism is provided for positively controlling the rate of rotation of the rollers. The rollers can effect lamination of the dough as they roll it.
U.S. Pat. No. 3,973,895 to Hayashi describes a method of rolling dough which is closely similar to that described in U.S. Pat. No. 4,113,412, but in which the roller assembly is provided with means for controlling the speed of the conveyor belt under the rollers.
U.S. Pat. No. 4,192,636 to Hayashi et al discloses another method of rolling dough which is similar to that described in the preceding patents and uses an endless belt carrying a plurality of rollers.
U.S. Pat. No. 4,056,346 to Hayashi describes a method of rolling dough in which the dough is first rolled by a multiple roller assembly of the same types as disclosed in the three preceding patents. However, in U.S. Pat. No. 4,056,346 the dough, after leaving the multiple roller assembly, passes under an additional roller which does not stretch the dough but limits the contraction of the dough which would otherwise occur due to its resiliency.
U.S. Pat. No. 4,178,147 to Hayashi discloses a method of stretching dough using a multiple roller assembly similar to that of U.S. Pat. No. 4,113,412 and other Hayashi patents discussed above. However, in U.S. Pat. No. 4,178,147 the conveyor belt lying beneath the multiple roller assembly in U.S. Pat. No. 4,113,412 is replaced by a series of rollers which are rotated to carry the dough in the desired direction. The resultant structure includes pairs of adjacent rollers on either side of the side, these pairs of rollers rotating in opposed directions.
The sheet formation stage of the multi-stage process used to produce puffed pastry and other laminated products is attended with serious difficulties. Because of the reduction in area of the sheet effected by the laminations, the sheet must be formed at a very high rate to allow modern commercial lamination, rolling and cutting equipment to operate at its optimum speed. On the other hand, since it is desired to produce a final laminated product containing a large number of very thin layers of dough, it is desirable that the sheet initially formed be thin, and it is difficult to form sufficiently thin layers of fat and dough having the necessary uniformity, especially since a relatively wide sheet, typically 14-50 cm. wide, is desired. The combination of the large width of the sheet and the thinness of the layers renders the sheet highly vulnerable to rupturing and tearing as it is formed and, if any tearing of the sheet occurs, leakage of the fat from the sheet may result, with costly interruptions to production, excessive scrap and possibly damage to processing machinery.
All the prior art techniques for sheet formation have serious disadvantages. The technique involved in U.S. Pat. No. 3,151,987, in which plastic shortening is applied to a sheet of paste, is difficult to operate at high speeds without using multiple dispensers for the paste and the plastic shortening, and thus the apparatus required tends to be elaborate and costly. In addition, it is difficult when using such multiple shortening dispensers to achieve uniformity and thickness in the multiple layers of paste and shortening, and because the shortening layers are exposed at the edges of the sheet there is a serious risk of leakage of shortening during the lamination and rolling stages of the process. The process described in U.S. Pat. No. 3,821,452, in which spherical particles comprising a fat center enrobed by a dough layer are flattened, is difficult to operate at sufficient speeds, tends to produce non-uniform layers of fat because of the way in which the spherical particle is stretched during flattening, and may result in leakage of the fat, especially if the platen is being operated at high speed. The process disclosed in U.S. Pat. No. 1,975,326 suffers from the same disadvantages as that disclosed in U.S. Pat. No. 3,151,987.
It might appear that one method for producing the necessary sheet of fat and dough at high speed would be coextrusion of fat and dough. and methods for such coextrusion are known. For example, U.S. Pat. Nos. 4,113,819, 4,266,920 and 4,416,910, all to Hayashi, describe apparatus and processes for manufacturing multi-layered dough materials comprising layers of dough and fat or oil, such as butter. These processes involve coextrusion of dough and fat through a die having concentric annular orifices to form a hollow tube in which an inner layer of fat is surrounded by an outer layer of dough. In U.S. Pat. Nos. 4,412,819 and 4,416,910, this tube is then collapsed under its own weight on to a first conveyor, which passes it under a rolling assembly comprising a plurality of rolls which are themselves carried around an endless belt. At the end of the first conveyor, the rolled sheet passes downwardly to an oscillating chute, which oscillates parallel to the direction of motion of the first conveyor, and are formed into a pile, comprising multiple plies of the sheet, on a second conveyor, which conveys it under second rolling assembly generally similar to the first one already described.
In the apparatus shown in U.S. Pat. Nos. 4,113,819 and 4,416,910 both orifices of the coextrusion die are annular. The patents discussed the possibility of using a die having orifices of flattened or rectangular form, but state that, since the elevation angles of various portions of the inner faces of the nozzles are considerably different from each other because of the required changes in the cross-section of the channels used to feed material to the orifices of such a flattened die, such flattened or rectangular orifices are to be avoided because the discharge speed is different between the middle and end portions of the rectangular orifices. Such changes in discharge speed would result in non-uniformity of the thickness of the layers of fat and dough forming coextruded tube, and might result in distortion or rupture of the tube. Also, if in accordance with the teachings of these patents annular dies producing a hollow cylindrical tube are used, and if this tube is to have the diameter desirable to produce a sheet of the desired width for high-speed production, the dies required are extremely large, cumbersome and expensive to form. Moreover, it is difficult to collapse a large diameter. thin-walled coextruded tube of the relatively soft fat and dough on to a moving conveyor belt at high speed without distorting or even rupturing the tube, which again will produce non-uniformities in the product and may result in interruption of production and leakage of fat from the sheet.
U.S. Pat. No. 3,572,259 to Hayashi discloses a process in which a cylinder of dough filled with a filler is coextruded in the same manner as in U.S. Pat. No. 4,113,819, and the coextruded cylinder is thereafter formed into double-layered spheres. A similar method, not restricted to the coextrustion technique of U.S. Pat. No. 4,113,819, is disclosed in U.S. Pat. No. 3,351,026 to Hayashi. For the reasons already discussed above in relation to U.S. Pat. No. 3,821,452, processes involving formation of spherical particles in which a filler is enrobed by dough and flattening these particles to form sheets cannot be operated at sufficient production rates and may cause problems in secured a sufficiently uniform product.
There is thus a need for an apparatus and process for coextrusion of fat and dough which is capable of producing a wide sheet at high production rates and with uniform thickness of the layers of fat and dough. This invention provides such an apparatus and process.